Multistage diaphragm vacuum servo

ABSTRACT

A HOUSING CONTAINS TWO AXIALLY SPACED VACUUM ACTUATED FLEXIBLE DIAPHRAGMS EACH SPRING BIASED TOWARDS THE OTHER AND CONTROLLING MOVEMENT OF A FORCE TRANSMITTER SECURED TO ONE OF THE DIAPHRAGMS, THE SPRING ASSEMBLY BIASING THE ONE DIAPHRAGM INCLUDING TWO SPRINGS OF DIFFERENT PRELOADS AND A SPRING RETAINER THAT IS LOCATED BETWEEN THE TWO SPRINGS AND OF A CONSTRUCTION PROVIDING TWO STAGE OPERATIONAL MOVEMENT OF THE ONE DIAPHRAGM IN ONE DIREACTION IN RESPONSE TO VACUUM CHANGES.

NOV. 9, 1971 G, R, M|| ER 3,618,473

MULTISTAGE DIAPHRAGM VACUUM SERVO Filed Feb. 2, 1970 VACUUM ,C v 6INVENTOR GIR/M0 /M/Zfl? ATTORNEYS United' States Patent O 3,618,473MULTISTAGE DIAPHRAGM VACUUM SERVO Gerald R. Miller, N orthville, Mich.,assignor to Ford Motor Company, Dearborn, Mich. Filed Feb. 2, 1970, Ser.No. 7,490 Int. Cl. F01b 19/02 U.S. Cl. 92-48 2 Claims ABSTRACT OF THEDISCLOSURE A housing contains two axially spaced vacuum actuatedflexible diaphragms each spring biased towards the other and controllingmovement of a force transmitter secured to one of the diaphragms, thespring assembly biasing the one diaphragm including two springs ofdifferent preloads and a spring retainer that is located between the twosp-rings and of a construction providing two stage operational movementof the one diaphragm in one direction in response to vacuum changes.

This invention relates, in general, to a multistage fluid motorconstruction. More specifically, it relates to a dual diaphragm vacuummotor assembly in which one of the diaphragms moves in a plurality ofstages.

This invention in particular is an improvement over the dual diaphragmfluid motor construciton of Ser. No. 858,567, Frank M. Kittredge, filedSept. 11, 1969; As stated in the latter application, anti-smogregulations relating to internal combustion engine exhaust emissioncontrols point out the desirability of selectively controlling theignition timing at all engine speed and load conditions. This is notonly to provide minimum engine exhaust hydrocarbon and other undesirableexhaust emissions, but good engine performance and economy as well.

The dual diaphragm actuator of Ser. No. 858,567 provides, among otherthings, normal engine ignition advance timing as a function of changesin carburetor spark port vacuum during part throttle engine operation.It does not, however, provide means for retarding the advance to permitoperation of the engine at a fixed spark setting, for example. Operationat such a setting has been found beneficial in further reducing theoutput of unburned hydrocarbons and other undesirable elements.

This invention, therefore, provides a dual diaphragm fluid motorconstruction in which the ignition timing advance is capable of beingmodulated in a plurality of stages, and the primary diaphragm is springloaded in a unique manner to provide the staging.

It is an object of the invention, therefore, to provide a multi-stagedual diaphragm vacuum motor actuator in which the movement of theactuator in one direction varies as a function of the changes in aplurality of sources of vacuum operatively acting on the actuator, and aplurality of spring forces.

It is another object of the inventionpto provide a dual diaphragm vacuumservo construction in which a plurality of preloaded springs bias one ofthe diaphragms in one direction in a manner causing multi-stageoperation of the servo.

Other objects, features and advantages of the invention will become moreapparent upon reference to the succeeding detailed description thereof,and to the drawings illustrating the preferred embodiment thereof,wherein;

FIG. 1"`is a cross sectional view of a vacuum servo mechanism embodyingthe invention; and

FIG. 2 graphically illustrates a typical travel movement of the actuatorof the servo shown in FIG. 1 with changes in vacuum level.

Ser. No. 858,567 shows and describes an engine ignition timing systemofthe type in which the present invention could be used. However, it willbecome apparent that it will have many other uses wherever a servocontrol of the type to be described is desired. Therefore, only theservo control per se will be described.

In general, the vacuum motor assembly 10` shown in FIG. l includes twoflexible diaphragms 12 and 14 mounted in a housing 16 and definingseparate vacuum chambers 18 and 20 to provide various control movementsof an actuating rod 22. Chamber 20 is connected by a hose or line 24 toa first source of varying vacuum, such as, for example, the vacuum of anengine intake manifold. The other chamber 18 is connected 'by a hose orline 26 to a source of vacuum that alternates from an essentially zerolevel to a maximum.

No controls are shown for varying the vacuum levels in chambers 18 and20l since they can be conventional, can be manually or automaticallyoperated, and the details and operation thereof are believed to beunnecessary for an understanding of the invention. Furthermore,reference may be had to Ser. No. 858,567 describing one such systemchanging the vacuum levels.

More specifically, the vacuum motor housing 16 in cludes a bell-like,hollow, left hand portion 28, and a donut-shaped, right hand portion 30,vthe latter having a stepped diameter central opening 32. Axiallybetween the two housing portions is a ring-like stop plate 34 contiguousto a ring-like stop plate 36. The latter has a stepped inner diameter 38defining, with stop plate 34, an annular groove 40. Projecting into andaxially movable within groove 40 is the bent edge 42 of a washer-likediaphragm retainer 44. The latter retainer, together with a semitoroidalshaped retainer 46, is clamped to the annular flexible diaphragm 14having a central aperture 48.

The diaphragm 14 extends across the hollow interior of the housing andis sealingly mounted at its outer edge between stop plate 36 and theflange on housing portion 30. It is sealingly clamped against thehousing at its inner edge. A spring 50 normally biases diaphragm 14 tothe position shown locating flange edge 42 against the face of stopplate 34. The diaphragm, together with the Walls of housing portion 30,defines the fluid or vacuum chamber 20.

The second flexible annular diaphragm 12 is sealingly mounted betweenhousing portion 28 and stop plate 34, and extends across the housing todefine with it the fluid or vacuum chamber 18 connected to hose 26. Thetwo housing portions and stop plates and diaphragms are fixedly securedtogether by means of an annular cap plate 54.

Rod 22, which, in the preferred installation, is a distributor advanceplate actuating rod, is fixedly secured to diaphragm 12 by means of twocup-shaped plates 56 and 58. Movement of the diaphra-grn in eitherdirection, therefore, will cause a corresponding pivotal movement of theconventional distributor advance plate (not shown). The radiallyoutermost bent edge of plate 56 at times is adapted to abut the inneredge of the diaphragm stop plate 44 to limit movement of the (primary)diaphragm 12 in one direction, for a purpose to be described later.

A spring assembly identified as a whole as 62 normally biases theprimary diaphragm 12 and rod 22 to the right to seat or abut edge 60against plate 44. The spring assembly seats at one end against acombination spring seat and guide plug l64 that is threaded into housing30. The plug also acts as an adjustable stop to limit movement ofdiaphragm 12 in a leftward direction, as will be explained more fullylater.

As thus `far described, the construction is the same as shown anddescribed in Ser. No. 858,567. Turning now to the invention, the springassembly 62 is con- ACC structed in a manner providing dual stageoperational movement of diaphragm 12 in a leftward direction.

More specifically, assembly 62 includes first and second axially alignedsprings 66 and 68. The adjacent end of the springs seat against thesides of a ring-like flange 70 projecting radially from a springretainer 72. The opposite end of spring7 66 seats against plug 64, whilespring 68 seats against the lip flange 74` of a spring guide 76.

Guide 76, which can be of elastomeric or plastic material, comprises asleeve having an internal annular boss 78. The latter defines a shoulder80 in the stepped diameter internal periphery. On the other hand, theretainer 72 comprises a plastic sleeve having four (only three shown)fiexible finger-like portions 82. The fingers, in an assembled conditionof the retainer and guide, extend laterally to a position inside sleeve76. Each finger has a hook-like part 84 projecting radially from itsouter periphery and adapted to cooperate with shoulder 80 constitutingan axial stop.

In effect, boss 78 of sleeve 76 and parts 84 of retainer fingers 82 areinterengaging portions axially slidably connected. To assemble, thefingers 82 are bent inwardly sufficient to clear the boss 78, insertedinto sleeve 76 through the hole defined by boss 78 and then released.The resiliency of the fingers returns them to the shape shown. Thisprevents complete separation of the two while permitting a limitedsliding movement between.

Intially, therefore, the preload of spring 68 separates retainer 72 fromguide 76 a maximum distance, as shown. The preload of spring 66maintains the retainer 72 and guide 76 against diaphragm retainer plate58, and biases the diaphragm against stop plate 44.

The preload of primary spring 66 is chosen to be of a lower value thanthat of second spring 68, for a purpose that will become clear later.Also, the preloads of both springs 66 and 68 are lower than the preloadof secondary diaphragm spring S0.

It will be clear that the preloads of the springs can be chosen to suitthe particular results desired, as will be explained in connection withFIG. 2, for example. Also, varying the axial extent or position of thestops will change the characteristics of operation of the servo.

FIG. 2 illustrates `graphically typical changes in travel distance ofrod 22 for changes in vacuum level from an initial setting. Assume, forexample, the vacuum level in chambers 18 and 20 initially is zero, or atatmospheric pressure. In operation, therefore, with the preloads of thesprings as described, the parts are positioned as shown. The preload ofsecondary spring `50 moves diaphragm 14 to the left and abuts edge 42against stop plate 34 to provide an initial position of rod 22 at O inFIG. 2..

Assume now that vacuum is applied only to chamber 18. Until the preloadof first spring 66 is overcome, an increase in vacuum produces nomovement of rod 22. This is represented by the horizontal line OA inFIG. 2. Upon increase in vacuum, once the preload of spring `66 isovercome, retainer 72 and guide 74, diaphragm 12 and rod 22 then willbegin moving to the left as a unit without compression of spring 68.Thus, as the vacuum in the primary chamber 18 increases, the rod 22 willmove progressively between the points A and B in FIG. 2. The slope ofthe curve will be determined by the rate of spring `66. Point Brepresents the position of diaphragm 12 when the retainer 72 hasbottomed against the end of plug 64. This ends the first stage ofmovement. Further increases in vacuum, therefore, produce no furtherleftward movement of the rod 22 until the preload of spring 68 isovercome. That is represented by the horizontal line BC in FIG. 2. Oncethis latter vacuum level is attained, the guide 76 begins moving axiallyon the fingers 82 by compressing spring 68. This is represented by theline CD in FIG. 2, the

l slope varying with the spring rate of spring 68. Finally, point Drepresents the end of stage two by the bottoming of guide 76 aginstretainer 72, which has previously bottomed against plug 64. Furtherincrease in vacuum produces no further leftward movement of rod 22, asindicated by the horizontal line DE in FIG. 2.

The action is reversed, of course, during a decrease 1n vacuum.

The movement of rod 22 in a rightward direction is the same as isalready fully described in Ser. No. 858,567. Therefore, only a briefdescription will be given. Assume, therefore, that there is no vacuum(atmospheric pressure) in chamber 18 and that we begin applying vacuumto chamber 20. Until the preload of secondary spring 50 is overcome, rod22 will remain stationary. Again, this is represented by the horizontaldistance OA in FIG. 2. As the vacuum increases above the preload of thespring, secondary diaphragm 14 will be drawn rightwardly until theflange 42 of plate 44 abuts stop plate 36. This is represented by thedotted line AF in FIG. 2. Further increases in vacuum, therefore, willnot cause a further travel of rod 22, as indicated by the horizontaldotted line FG.

Assume now, therefore, that vacuum is applied in a controlled manner toboth vacuum chambers 18 and 20 in a varying manner. It will be clearfrom a consideration of FIG. 2 that the two curves A-E and A-G can becombined to provide a varying slope curve (not shown).

Thus, from the above, it will be seen that by varying the levels ofvacuum in the primary and secondary vacuum chambers 18 and 20 in aselective manner, and/or varying the preloads of the springs 50, 66 and68, and/ or varying the spring rate of the springs and/or varying theaxial locations of the stops and other adjustable changes previouslydescribed, that the curves shown in FIG. 2 can be made to assumesubstantially any number of shapes desired to provide a particulardesired movement of rod 22 in either or both directions.

While the invention has been illustrated in its preferred embodiment inthe drawings, it will be clear to those skilled in the arts in which itpertains that many changes and modifications may be made thereto withoutdeparting from the scope of the invention.

I claim:

1. A multistage fluid motor assembly comprising, a housing, a pair offlexible annular diaphragm members each mounted in said housing for anindependent movement relative to the other and each with said housingdefining a different vacuum chamber, means connecting each of saidchambers to separate source of fiuid varying from a maximum essentiallyatmospheric pressure level to a minimum sub-atmospheric pressure orvacuum level for reciprocable movement of each of said members as afunction of the changes in vacuum acting thereon, spring means biasingeach of said diaphragm members towards the other, and movable forcetransmitting means operatively connected to one of the said pair ofdiaphragm members engaging at times with the other of said members uponmovement of the said one ember in one direction for limiting themovement of the said one member in said one direction in a variablemanner as a function of the position of the said other of said members,said one diaphragm member being `movable in the opposite direction as afunction of the changes in vacuum in said chambers and the forces ofsaid spring means, said spring means biasing said one diaphragmincluding first and second springs serially arranged, said first springproviding a lesser force then said second spring whereby said onediaphragm moves in stages as the vacuum forces successively overcome thedifferent forces of said springs, said spring means biasing said onediaphragm including a spring retainer floatingly mounted between saidrst and second springs, an increase in net vacuum force acting in theopposite direction on said one diaphragm to a level above the forceexerted by said first spring progressively moving said retainer andforce transmitting means in the said opposite direction at `a ratevarying as a function of the spring rate of said rst spring, second seatmeans for the other end of said second spring, and means interconnectingsaid retainer and second seat means -for a limited relative movementtherebetween, the force of said second spring initially biasing saidretainer. and second seat means apart, an increase in the net actuatingforce on said one diaphragm above the force of said second spring movingsaid second seat means towards said retainer thereby permitting movementof said force transmitting means in the said opposite direction, saidsecond seat means comprising a sleeve having an internal projection,said retainer having a springable, deformable finger with a hook-likeportion slidable initially Linto said latter sleeve by springing of saidportion over and past said projection thereby preventing disengagementof said sleeve and portion while permitting axial sliding movementtherebetween.

2. A multistage fluid motor assembly comprising, a housing, a pair oftiexible annular diaphragm members each mounted in said housing for anindependent movement relative to the other and each with said housingdening a different vacuum chamber, means connecting each of saidchambers to a separate source of iluid varying from a maximumessentially atmospheric pressure level to a minimum sub-atmosphericpressure or vacuum level for reciprocable movement of each of saidmembers as a function of the changes in vacuum acting thereon, springmeans biasing each of said diaphragm members towards the other, andmovable force transmitting means operatively connected to one of thesaid pair of diaphragm members engaging at times with the other of saidmembers upon movement of the said one member in one direcvtion forlimiting the movement of the said one member in said one direction in avariable manner as a function of the position of the said other of saidmembers, said one diaphragm member being movable in the opposite'direction as a function of the changes in vacuum in said chambers andthe forces of said spring means, said spring means biasing said onediaphragm including first and second springs serially arranged, said rstspring providing a lesser force than said second spring whereby said onediaphragm moves in stages as the vacuum forces successively overcome thedifferent forces of said springs, said spring means biasing said onediaphragm including a spring retainer oatingly mounted between said rstand second springs, an increase in net vacuum force acting in theopposite direction on said one diaphragm to a level above the forceexerted by said first spring progressively moving said retainer andforce transmitting means in the said opposite direction at a ratevarying as a function of the spring rate of said first spring, secondseat means for the other end of said second spring, and meansinterconnecting said retainer and second seat means for a limitedrelative movement therebetween, the force of said second springinitially biasing said retainer and second seat means apart, an increasein the net actuating force on said one diaphragm above the force of saidsecond spring moving said second seat means towards said retainerthereby permitting movement of said force transmitting Imeansin theopposite direction, said retainer having an axially extending portionthat is flexible and the end of which is yieldingly movable in a lateraldirection, said portion having a projection on the end extendingradially outwardly, said second seat means comprising a stepped diametersleeve defining an internal shoulder, said projection being sprunginwardly in response to movement into said sleeve past said shoulder andsubsequently returned outwardly to its free state whereby separatingmovement of said sleeve and retainer is prevented and limited axialsliding -relative movement is permitted.

References Cited UNITED STATES PATENTS 2,379,306 6/1945 Larson et al.92-130 X 3,082,792 3/ 1963 Jenkins 92-98 RD 3,385,275 5/ 1968 Burnia etal 92-64 UX 3,508,469 4/ 1970 Williams 92-63 MARTIN P. SCHWADRON,Primary Examiner I. C. COHEN, Assistant Examiner U.S. C1. X.R.

